In heating objects or materials such as meat and the like whose taste is much affected by its heating temperature, or in heating a comparatively large amount of material in a microwave oven, it is necessary to detect the heating temperature of these materials being heated. For this and other reasons, in some prior art microwave ovens, a temperature detecting device is provided in the oven.
One of the most commonly used temperature detecting devices includes a probe or temperature detector which is of a comparatively thin needle shape and has a thermal sensitive member incorporated therein, a handle which is comparatively large in size for facilitating easy holding thereof by an operator, a cable for transmitting a detected temperature signal to a control unit provided outside the heating cavity of the microwave oven, and a flexible member extending from the handle to any wall of the heating cavity. To carry out the detection of the temperature of the objects or materials being heated, the operator holds the temperature detecting device and inserts the probe into the object to be heated. A temperature signal is then continuously transmitted towards the control unit.
In order to detect the temperature of the object with accuracy and also in order to facilitate the insertion of the probe into the object, the probe of the above described type is comparatively small in size and has a heat capacity which is as small as possible, that is, the probe is designed to have as small a mass as possible. On the other hand, the handle as well as the cable of the detecting device are not necessarily formed as such a small size, and are preferably a comparatively large size for easy holding. Therefore, the temperature detecting device of the conventional type has its weight mostly occupied by the handle. This being the case, the detecting device is apt to lose its balance during the use thereof.
Accordingly, there has been a disadvantage in conventional temperature detecting devices of the above described type, because the temperature detecting device may fall from the inserted position or may not possibly be used with objects which are liquid or of comparatively small size. When the detecting device is improperly used for detecting the temperature of liquid and falls from the container, an undesirable arc may be produced between the probe, which is made of metal, and the wall of the heating cavity upon contact therebetween. The probe, especially the thermal sensitive member, and the wall of the cavity may thereby be accidentally damaged.
Another known type of the temperature detecting device is not provided with the cable, but has a gauge for directly indicating the temperature of the object. This type of detecting device, nevertheless, still has disadvantages similar to those described above.